Description
Factory-Direct Q235 Square Tubes — Every 100×100 to 500×500mm welded section rolls through our in-house lab before container loading, eliminating third-party markup and quality guesswork.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q195, Q235, Q345 |
| Standard | ASTM, JIS, DIN |
| Section Shape | Square |
| Size Range | 100×100mm – 500×500mm |
| Wall Thickness | 0.5 – 25 mm |
| Length | 6 – 12 m |
| Technique | Hot Rolled / Cold Rolled |
| Surface Treatment | Hot Rolled, Oiled or Non-oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Industrial plant steel frames, pipe rack supports, equipment platforms |
| Construction Companies | High-rise building column grids, scaffolding uprights, bridge bearing members |
| Machinery Manufacturers | Conveyor frame structures, crane boom sections, hydraulic press bases |
| Infrastructure Developers | Sound barrier posts, solar panel mounting structures, highway sign gantries |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a Q235 welded square steel tube means the difference between passing structural inspection and tearing down a completed frame.
I watched a Southeast Asian contractor lose an entire container of 300×300 rectangular tubes because the wall thickness measured 8.5mm instead of the specified 10mm on arrival. The mill certificate looked flawless, but the project engineer’s ultrasonic gauge told a different story. When tolerance drifts beyond acceptable limits, load-bearing calculations become meaningless, weld connections weaken, and the entire procurement turns into a liability. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Q235 Square Tubes to Structural Load Requirements
The Q235 welded square steel tube in 100×100mm to 500×500mm dimensions covers the mid-range structural spectrum where yield strength meets economy. For building frames carrying vertical loads below 235 MPa design stress, Q235 delivers adequate performance without the cost premium of higher grades. The 0.5–25mm wall thickness range allows engineers to optimize weight versus load capacity — thinner walls for non-load-bearing scaffolding, heavier sections for primary column members. Our production lines hold 2,800+ specifications in inventory, so a contractor ordering mixed sizes for a single project gets consolidated shipping rather than fragmented sourcing from multiple mills.
Engineering Compliance and Certification Pathways
Structural steel procurement for EU projects requires CE certification under EN 10210 or EN 10219, while North American specifications typically reference ASTM A500. The Q235 grade maps roughly to S235JR in the European system and Gr. B in ASTM, but equivalence is not automatic — chemical composition limits and mechanical property testing methods differ across standards. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and American ASTM standards] Our mill issues CE certificates for EN-compliant shipments and provides full mill test certificates documenting heat-by-heat chemistry. For projects requiring third-party verification, SGS or BV inspection reports accompany the cargo, ensuring customs clearance proceeds without material compliance disputes.
Understanding Q-Series Steel Grades and Welded Tube Manufacturing
The Q in Q235 stands for “yield” in Chinese steel designation, where the number represents minimum yield strength in MPa. Q195 offers lower strength but superior formability for cold bending operations, while Q345 provides higher load capacity for demanding structural applications. Welded square tubes are formed by rolling steel strip into square profile and welding the seam longitudinally — this process allows tight dimensional control and consistent wall thickness across the 6–12m length range. Hot rolled tubes suit heavy structural work where surface finish is secondary, while cold rolled sections deliver smoother surfaces for visible architectural applications. The oiled surface treatment prevents rust during transit and storage, particularly critical for ocean shipments to tropical climates where condensation accelerates corrosion.
The Hidden Price of Unverified Material Certificates
Ordering Q235 welded square steel tube based on paper certificates alone invites three categories of failure: dimensional non-conformance that triggers site rejection, chemistry mismatches that compromise weldability, and missing traceability that blocks customs clearance. When a supplier cannot provide heat-number traceability back to the original slab, the entire batch becomes suspect. Engineering inspectors increasingly demand mill test certificates showing actual test values rather than specification minimums, and projects without proper documentation face delays measured in weeks, not days. [NEED_CITE: structural steel procurement documentation requirements for international construction projects]
Why Engineers Source Q235 Welded Square Steel Tube from Jinan
Our factory operates three dedicated production lines with in-house physical and chemical laboratories — every heat undergoes tensile testing, chemical analysis, and dimensional verification before release. We hold 41 invention patents including proprietary sharp-corner rectangular tube technology, and our 2,800+ specification inventory means contractors source complete project quantities from a single point rather than coordinating multiple vendors. CE EN 10210/10219 certification, ISO 9001:2015 quality management, and SGS/BV third-party inspection capabilities ensure compliance across EU, North American, and Asian markets. Professional loading plans optimize container utilization for the 100×100mm to 500×500mm size range, and our logistics team coordinates FOB, CIF, or DDP delivery to 50+ countries with real-time shipment tracking.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Mn, Si, S, P limits) and yield strength per GB/T 700 standard
- CE certificate confirming EN 10210/EN 10219 compliance for European structural steel applications
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying dimensional accuracy and surface quality before shipment
- Material traceability documentation linking each bundle to original heat number and slab certification
- Customs clearance package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235 welded square tubes bundled with steel strips and edge protectors to prevent corner damage during handling
- Oiled surface treatment applied before bundling to prevent rust formation during ocean transit to tropical destinations
- Container loading plans optimized for 100×100mm to 500×500mm sections, maximizing weight utilization within 6m and 12m length configurations
- Heat number and steel grade markings stenciled on each bundle for site identification and traceability verification
- FOB Jinan/Qingdao port delivery with CIF and DDP options available for project sites across Southeast Asia, Middle East, and Africa
- Custom cutting to specific lengths available for construction projects requiring precise member dimensions without on-site waste
Securing Your Q235 Square Tube Quotation with Full Documentation
Submit your specification sheet including size, wall thickness, quantity, steel grade preference, and destination port — we respond within 12 hours with pricing, production timeline, and applicable certification details. For non-standard dimensions outside the 100×100mm to 500×500mm range, our technical team provides custom manufacturing proposals with MOQ flexibility. Confirm your certification requirements (CE, ASTM, or GB standard) and third-party inspection needs before contract signing to ensure smooth customs clearance at destination.
Frequently Asked Questions
Q: Can Q235 steel grade be used for projects requiring ASTM A500 specification?
A: Q235 provides similar yield strength to ASTM A500 Grade B, but chemical composition limits differ between Chinese GB and American ASTM standards. For projects requiring strict ASTM compliance, we produce to ASTM A500 specification with full mill test certificates documenting conformity.
Q: What is the minimum order quantity for custom non-standard square tube sizes?
A: Standard sizes from our 2,800+ specification inventory carry a 5-ton MOQ. Custom non-standard dimensions require minimum 20 tons per size to justify production line setup, with typical lead times of 25-35 days depending on specification complexity.
Q: How do you ensure wall thickness tolerance meets ±1% requirement?
A: Every production batch undergoes ultrasonic thickness measurement at multiple points along length and around perimeter. Our in-house laboratory records measurements against heat number, and mill test certificates include actual thickness values rather than specification ranges.
Q: Can you provide third-party inspection before container loading?
A: Yes, we coordinate SGS or BV inspection at our facility before shipment. The inspection covers dimensional verification, surface quality assessment, and witness testing. Inspection reports accompany shipping documents for customs and project handover.
Q: What surface treatment options are available for corrosion protection?
A: Standard delivery includes hot rolled condition with oil coating for transit protection. For enhanced corrosion resistance, we offer hot-dip galvanizing after fabrication, with zinc coating thickness meeting EN 10240 or ASTM A123 requirements depending on destination market standards.
Get Your Q235 Welded Square Steel Tube Quote with Mill Test Certificate
Send specifications to admin@sdxjysteel.com or WhatsApp +86 188 5315 7756 for pricing, certification details, and delivery timeline to your project site.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
www.sdxjysteel.com
